EXCHANGE 


REACTIONS    BETWEEN    POTASSIUM 

AMIDE   AND    CERTAIN    SALTS 

OF  NICKEL  AND  CHROMIUM 

IN  LIQUID  AMMONIA 

SOLUTION 


A  THESIS 

SUBMITTED  TO  THE   DEPARTMENT  OF  CHEMISTRY  AND  THE 

COMMITTEE  ON  GRADUATE  STUDY  OF  THE  LELAND 

/  STANFORD  JUNIOR  UNIVERSITY  IN  PARTIAL 

'  FULFILMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR 

OF  PHILOSOPHY 


GEORGE  S.  BOHART 
March,  1915 


\ 


UNlVtKS 


Easton,  Pa.: 
EscHENBACH  Printing  Co. 
1915 


REACTIONS    BETWEEN    POTASSIUM 

AMIDE   AND    CERTAIN    SALTS 

OF  NICKEL  AND  CHROMIUM 

IN  LIQUID  AMMONL\ 

SOLUTION 


A  THESIS 

SUBMITTED  TO  THE   DEPARTMENT  OF  CHEMISTRY  AND  THE 

COMMITTEE  ON  GRADUATE  STUDY  OF  THE  LELAND 

STANFORD  JUNIOR  UNIVERSITY  IN  PARTIAL 

FULFILMENT  OF  THE  REQUIREMENTS 

FOR  THE  DEGREE  OF  DOCTOR 

OF  PHILOSOPHY 


BY 

GEORGE  S.  BOHART 
March,  19 15 


Easton,  Pa.: 
EscHENBACH  Printing  Co. 
1915 


REACTIONS    BETWEEN    POTASSIUM    AMIDE    AND 
CERTAIN    SALTS    OF    CADMIUM,    NICKEL 
AND  CHROMIUM  IN  LIQUID  AMMONIA 
SOLUTION^ 


BY  GEORGE  S.  BOHART 

CONTENTS 

I.  INTRODUCTION.  I.  The  Ammonia  System  of  Acids,  Bases  and  Salts. 
2.  Amphoteric  Metallic  Amides.    3.  Object  of  this  Investigation. 

II.  MANIPULATION  OF  WQUID  AMMONIA  SOLUTIONS  AND  DESCRIPTION  OF 
APPARATUS   USED. 

III.  ACTION     OF     POTASSIUM     AMIDE     ON     CADMIUM     SALTS.       J.    PotaSsium 

Ammonocadmiate,  Cd{NHK)i.2NHz.  2.  Cadmium  Amide,  Cd^NH-iji.  j.  Cad- 
mium Nitride,  Cd^N^. 

IV.  ACTION    OF    POTASSIUM    AMIDE    ON    POTASSIUM    CYANONICKELATE.      I. 

Preparation  of  Pure  Potassium  Cyanonickelate,  Ni{CN)iK2.  2.  Compound  No.  i. 
A  Complex  Product  of  the  Empirical  Formula  Ni3N2H2K4{CN)s.8NH3  and  its 
Deammonation  Product,  Ni3N2H2Ki{CN)&.  3.  Compound  No.  2.  A  Mixed 
Cyanonickelate-ammononickelate  of  Potassium,  K{CN)2NiNHK.  4.  Compound 
No.  3.     A    Complex   Compound   of  the  Empirical   Formula   Ni3NnH22KT{CN)2. 

V.  ACTION     OF     POTASSIUM     AMIDE     ON     NICKEL     SULFOCYANATE.       I.    Am- 

monated  Nickel  Sulfocyanate.  2.  Nickel  Sulfocyanate  with  Four  Molecules  of 
Ammonia,  Ni{SCN)2.4NH3.  3.  Nickel  Sulfocyanate  with  Three  Molecules  of 
Ammonia,  Ni{SCN)2:3NHs.  4.  Nickel  Sulfocyanate  with  Two  Molecules  of 
Ammonia,  Ni(SCN)2.2NH3.  5.  Nickel  Sulfocyanate  with  Five  and  a  Half  Mole- 
cules of  Ammonia,  Ni(SCN)2.5^/2NH3.  6.  Nickel  Sulfocyanate  with  Eight  and 
a  Half  Molecules  of  Ammonia,  Ni{SCN)2-8^/2NH3.  7.  Potassium  Ammono- 
nickelate,  Ni2N3Ki.6NH3.     8.  Nickel  Amide,  NiiNHi) 2.     9.  Nickel  Nitride,  NizN 2- 

VI.  ACTION  OF  POTASSIUM  AMIDE  ON  AMMONIUM  CHROMIUM  SULFOCYANATE, 

NH4Cr(SCN)4.2NH3. 

VII.  SUMMARY. 

I.    Introduction 

I.  The  Ammonia  System  of  Acids,  Bases  and  Salts. — In 
two  important  papers,^  Franklin  has  developed  in  detail  an 
ammonia  system  of  acids,  bases  and  salts.  He  has  called 
attention  to  the  fact  that  the  acid  amides,  the  metallic  amides 
and  the  metallic  derivatives  of  the  acid  amides  are  formally- 
related  to  ammonia  as  the  familiar  oxygen  acids,  bases  and 


1  The  author's  thesis  presented  to  the  Department  of  Chemistry  of  the 
Leiand  Stanford  Junior  University  in  partial  fulfillment  of  the  requirements 
for  the  degree  of  Doctor  of  Philosophy. 

2  Jour.  Am.  Chem.  Soc.,  27,  820  (1905);  Am.  Chem.  Jour.,  47,  285  (1912). 


335897 


un>KRU 


538  George  S.   Bohart 

salts  are  related  to  water  and  he  has  shown  that  these  substances 
actually  exhibit  in  liquid  ammonia  the  distinctive  properties 
of  acids,  bases  and  salts  respectively.  Acid  amides  in  liquid 
ammonia  solution  show  an  acid  reaction  toward  phenolph- 
phthalein;  they  react  with  certain  metals  with  the  evolu- 
tion of  hydrogen  and  with  metallic  amides,  imides  and  nitrides 
in  a  manner  strictly  analogous  to  the  action  of  aqueous  solu- 
tions of  oxygen  acids  on  metals,  metallic  hydroxides  and 
oxides. 

2.  Amphoteric  Metallic  Amides. — A  further  analogy  be- 
tween the  ammonia  and  water  systems  is  found  in  the  ampho- 
teric behavior  of  certain  metallic  amides  which  recalls  the 
familiar  behavior  of  zinc,  lead  and  aluminum  hydroxides 
towards  acids  and  strong  bases.  Fitzgerald^  and  Franklin^ 
have  shown  that  just  as  zinc  hydroxide  dissolves  in  aqueous 
solutions  of  potassium  hydroxide  to  form  potassium  (aquo) 
zincate  in  accordance  with  the  equation, 

Zn(0H)2  +  2KOH  =  Zn(0K)2  +  2H2O, 
so  zinc  amide  is  converted  into  an  ammonozincate  of  potas- 
sium by  the  action  of  a  liquid  ammonia  solution  of  potas- 
sium amide  on  zinc  amide  as  represented  by  the  equation, 
Zn(NH2)2  +  2KNH2  =  Zn(NHK)2  -f  2NH3. 

An  ammonoplumbite  of  potassium^  corresponding  to  the  aquo 
plumbite  of  potassium  has  also  been  prepared. 

It  has  been  further  found  in  this  laboratory  that  potas- 
sium amide  in  liquid  ammonia  solution  reacts  with  cuprous 
imide  to  form  an  ammonocuprite,  ^  with  thaUium  nitride  to 
form  an  ammonothallite^  and  with  magnesium  amide  to  form 
an  ammonomagnesate,^  three  compounds  of  the  ammonia 
system  whose  aquo  analogs  are  unknown. 

J.  Object  of  this  Investigation. — The  work  here  described 


*  Jour.  Am.  Chem.  Soc,  29,  660  (1907). 
'  Ibid.,  29,  1274  (1907). 

'  Jour.  Phys.  Chem.,  15,  509  (191 1). 

^  Jour.  Am.  Chem.  Soc,  34,  1501  (1912). 

*  Jour.  Phys.  Chem.,  16,  682  (1912). 

«  Jour.  Am.  Chem.  Soc,  35,  1455  (1913). 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.  539 

was  undertaken  for  the  purpose  of  studying  the  action  of 
Hquid  ammonia  solutions  of  potassium  amide  on  certain 
salts  of  cadmium,  nickel  and  chromium  with  the  object  in 
view  of  adding  several  new  metalUc  amides,  imides  or  nitrides 
to  the  Hmited  number  of  such  compounds  already  known,  and 
to  determine  whether  cadmium,  nickel  and  chromium  com- 
pounds similar  to  the  ammonozincate  mentioned  above  might 
be  prepared. 

II.    Manipulation   of  Liquid   Ammonia  Solutions   and   De- 
scpiption  of  Apparatus  Used 

Since  liquid  ammonia  has  a  low  boiling  point,  special 
forms  of  apparatus  must  be  used  to  control  the  high  pressures 
which  result  at  ordinary  temperatures.  A  brief  description 
of  the  apparatus  and  manipulation  follows : 

A  reaction  tube  of  the  form  shown  in  Fig.  i  is  connected 
with  a  cylinder  of  liquid  ammonia  by  means  of  a  lead  tube  (e) 
and  a  sealing  wax  joint  (c).  The  reaction  tube  is  thoroughly 
dried  by  heating  while  a  stream  of  ammonia  gas  passes  through 
first  one  branch  and  then  the  other.  While  the  gas  is  still 
flowing,  (a)  is  corked  and  the  required  amount  of  potassium 
is  inserted  at  (b)  by  cutting  off  portions  of  the  potassium  tube^ 
previously  prepared  and  calibrated.  A  small  amount  of 
platinum  black  is  dried  and  added,  after  which  the  cork  is 
transferred  from  (a)  to  (b)  and  the  small  tube  is  sealed  off 


^  In  order  to  purify  the  potassium  which  is  employed  in  these  reactions 
a  glass  tube  {bd),  Fig.  2,  about  two  centimeters  in  diameter  is  drawn  down  and 
welded  to  a  long  tube  having  a  diameter  which  will  permit  its  introduction  into 
the  reaction  tube.  The  slender  tube  is  fused  shut  at  (a)  and  a  loosely  fitting 
glass  plug  is  introduced  at  (d),  nearly  closing  the  opening.  Pieces  of  potassium 
are  removed  from  the  oil  in  which  they  are  kept,  dried  between  pieces  of  ab- 
sorption paper  and  dropped  into  the  large  tube.  Enough  is  added  to  fill  the 
slender  tube  when  molten.  A  one-hole  rubber  stopper  provided  with  a  piece 
of  glass  tubing  closes  the  opening  at  (b)  and  the  apparatus  is  connected  to  a 
suction  pump  by  means  of  heavy  walled  tubing.  After  a  good  vacuum  has  been 
produced  the  apparatus  is  heated  from  (a)  to  (b)  until  the  potassium  is  molten. 
Air  is  allowed  to  enter  at  (b)  whereby  the  pure  liquid  metal  is  forced  into  the 
slender  tube,  impurities  having  been  caught  by  the  plug  at  (d).  The  tube 
{ad)  is  removed  and  calibrated  by  weighing  a  measured  length  before  and  after 
dissolving  the  potassium  in  alcohol. 


540 


George  S.  Bohart 


as  illustrated  at  (6),  Fig.  3.  The  gas  pressure  necessary  to 
give  the  seal  a  rounded  end  of  uniform  thickness  is  obtained 
by  momentarily  closing  the  opening  at  (a)  with  the  finger 
while  the  glass  is  soft.  A  slender  glass  tube  containing  the 
metalUc  salt  which  is  to  react  with  potassium  amide  is  now 


Liquid 
ammonia 
reservoir  g 


5ucfion  ifn 


FIG.  5 


introduced  through  (a)  and  its  contents  forced  into  the  main 
apparatus  with  the  aid  of  a  fairly  snugly  fitting  glass  rod. 
The  opening  (a)  is  then  corked  at  the  same  time  as  the  key 
of  the  stopcock  is  removed.  The  leg  (a)  is  sealed  off  and 
blown  into  shape  by  carefully  placing  a  finger  and  thumb  over 
the  openings  left  by  the  removal  of  the  stopper  after  which 
the  latter  is  replaced. 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.         541 

By  placing  the  reaction  tube  (Fig.  3)  in  ice  water  and 
opening  the  valve  of  the  cylinder,  ammonia  distils  over  and 
condenses  in  both  legs.  When  the  liquid  first  comes  in  con- 
tact with  the  potassium  a  bright  orange  or  fiery  red  color  is 
produced  which  gives  place  to  a  deep  blue  solution  with  greater 
dilution.  A  rapid  evolution  of  hydrogen  gas  occurs  in  ac- 
cordance with  the  equation: 

2K  +  2NH3  =  2KNH2  +  H2 
The  platinum  black  greatly  increases  the  speed  of  the  reaction, 
reducing  the  time  required  for  completion  from  weeks  or 
months  down  to  a  half  hour  or  less  depending  on  the  amount 
and  efficiency  of  catalyzer  used.  When  the  reaction  is  com- 
plete the  solution  possesses  a  transparent,  pale  yellow  ap- 
pearance. 

Upon  pouring  the  potassium  amide  solution  into  the 
solution  of  the  metalUc  salt,  the  action  between  the  amide 
and  the  salt  may  be  observed.  If  the  product  is  relatively 
insoluble  it  may  be  obtained  free  from  other  compounds 
formed  in  the  reaction  by  repeated  washing  with  pure  liquid 
ammonia.  This  is  accompHshed  by  placing  the  leg  (a), 
Fig.  3,  in  ice  water  while  (6)  is  immersed  in  tepid  water. 
Pure  ammonia  distils  over  and  after  stirring  and  allowing  the 
precipitate  to  subside  the  supernatant  Uquid  is  decanted  back 
into  (6) .  Three  or  four  washings  are  sufficient  for  a  crystalline 
product,  but  it  is  often  necessary  to  repeat  the  operation 
fifteen  to  twenty  times  when  a  flocculent  substance  is  being 
washed. 

After  the  precipitate  has  been  thoroughly  washed  in  this 
manner  the  stopcock  is  opened  slightly  to  allow  the  am- 
monia to  slowly  escape.  When  no  more  gas  escapes  the  ap- 
paratus is  connected  to  the  ammonia  reservoir  by  means  of 
a  "T"  tube.  Fig.  4,  and  a  slow  flow  of  gas  is  started  to  pre- 
vent any  air  finding  its  way  into  the  reaction  tube.  The  stop- 
cock is  now  opened  wide  and  the  leg  containing  the  washings 
is  sealed  off  at  its  upper  end.  The  other  leg  which  contains 
the  product  is  evacuated  and  weighed.  By  placing  the  nozzle 
of  the  stopcock  beneath  the  surface  of  the  solvent  to  be  used 


542  George  S.  Bohart 

and  opening  the  stopper,  liquid  is  drawn  in.  With  the  aid 
of  the  apparatus  shown  in  Fig.  5  the  solution  of  the  compound 
is  drawn  into  the  flask  (a).  The  reservoir  (6)  is  employed 
for  safety. 

The  solution  is  now  removed  to  a  calibrated  flask  and 
later  divided  into  any  desired  number  of  aliquot  parts,  while 
the  tube  is  washed  first  with  alcohol,  then  with  ether  and 
finally  evacuated  and  weighed.  The  difference  between  the 
two  weighings  of  this  tube  is,  of  course,  equal  to  the  weight 
of  the  compound. 

III.  Action  of  Potassium  Amide  on  Cadmium  Salts 
I.  Potassium  Ammonocadmiate ,  Cd{NHK)i.2NHz. — Con- 
sidering the  fact  that  cadmium  hydroxide  is  not  known  to 
possess  amphoteric  properties  it  was  somewhat  of  a  surprise 
to  find  that  a  compound  represented  by  the  above  formula, 
instead  of  the  amide,  imide  or  nitride,  results  from  the  treat- 
ment of  a  soluble  salt  of  cadmium  with  an  excess  of  potas- 
sium amide  in  liquid  ammonia  solution.  The  behavior  of 
cadmium  was  found  to  follow  that  of  zinc  in  this  respect. 
Cadmium  iodide  with  ammonia  of  crystallization, 
.Cdl2.4NH3,  is  almost  insoluble  in  liquid  ammonia,  but  when 
crystals  of  this  substance  are  brought  into  contact  with  an 
excess  of  potassium  amide  solution  they  are  gradually  re- 
placed by  a  light,  flocculent  mass  which  subsides  very  slowly 
and  incompletely.  After  washing  this  substance  thoroughly 
to  remove  the  soluble  potassium  iodide  formed  in  the  reaction, 
it  is  dissolved  in  dilute  hydrochloric  acid  and  removed  from 
the  tube  in  the  manner  described  earlier  in  this  paper. 

In  the  preparation  of  Samples  I,  II  and  III,  cadmium  iodide 
was  used.  For  preparing  Sample  IV  potassium  cyanocad- 
miate,  on  account  of  its  ready  solubility,  was  substituted 
for  cadmium  iodide.  When  treated  with  an  excess  of  potas- 
sium amide,  the  double  cyanide  yields  a  white  precipitate 
closely  resembling  that  obtained  with  the  use  of  cadmium 
iodide.  All  the  preparations  were  heated  to  50°  in  vacuo 
before  removal  from  the  preparation  tube  for  analysis. 
Analytical  results : 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        543 

I.  One-fourth  of  the  specimen  which  weighed  0.4070 
g  gave  0.0455  S  Cd  by  electrolysis.  One-half  gave  0.0442 
gN. 

II.  One-fourth  of  0.2221  g  of  substance  gave  0.0455  K 
CdS04;  another  fourth  gave  0.0118  g  N;  and  one-half  gave 
0.0769  g  K2SO4. 

III.  One-half  of  0.2978  g  of  substance  gave  0.1230  g 
CdS04  and  0.1038  g  K2SO4.     One-fourth  gave  0.0161  g  N. 

IV.  One-hah  of  0.2841  g  of  substance  gave  0.1193  g 
CdS04  and  0.0959  g  K2SO4.     One-half  gave  0.0305  g  N. 


Calculated  for 
Cd(NHK)2.2NH3 

Found 

I 

II 

III 

IV 

Cd 

N 
K 

44.1 
22.0 
30.7 

44-7 
21 .7 

44.2 
21.3 
311 

44- 5- 
21 .6 

313 

45-2 
21.5 
30.3 

The  results  of  these  analyses  thus  show  the  empirical 
formula  of  the  compound  to  be  CdN4H8K2.  The  compound 
may  be  represented  by  the  formulas:  Cd(NHK)2.2NH3, 
Cd(NH2)2..2KNH2,  or,  after  Werner,  Cd(NH2)4K2.  The  re- 
actions involved  are  represented  by  the  equations : 

Cdl2  -f  4KNH2  =  Cd(NHK)2.2NH3  -\-  2KI 
K2Cd(CN)4  +  4KNH2  =  Cd(NHK)2.2NH3  +  4KCN. 

Potassium  ammonocadmiate  has  been  obtained  as  a  white, 
flocculent  material  which  turns  somewhat  gray  under  the 
influence  of  light.  It  is  insoluble  in  liquid  ammonia  and  shows 
no  tendency  to  assume  a  crystalline  form  as  does  potassium 
ammonozincate.  When  brought  into  contact  with  water  it 
reacts  with  the  generation  of  considerable  heat  and  the  forma- 
tion of  ammonia,  potassium  hydroxide  and  cadmium  hydroxide 
as  represented  by  the  equation : 

Cd(NHK)2.2NH3  -\-  4H2O  =  Cd(0H)2  -\-  2KOH  +  4NH3 

2.  Cadmium  Amide,  Cd{NH 2)2- — When  either  cadmium 
sulfocyanate  or  potassium  cyanocadmiate  in  solution  in  liquid 


544 


George  S.  Bohart 


ammonia  is  treated  with  potassium  amide  in  an  amount  not 
exceeding  one  equivalent,  a  white  precipitate  forms  which 
settles  rather  rapidly.  After  prolonged  washing  by  decanta- 
tion  it  begins  to  disperse  throughout  the  liquid  in  a  colloidal 
condition.  This  tendency  is  probably  due  to  the  fact  that 
the  concentration  of  the  electrolyte  has  been  reduced  almost 
to  zero  by  the  washing  process. 

Three  of  the  specimens  of  cadmium  amide  analyzed  were 
prepared  from  cadmium  sulfocyanate.  Sample  IV  was  ob- 
tained by  the  action  of  potassium  amide  on  potassium  cyano- 
cadmiate.  Both  of  these  cadmium  salts  are  abundantly 
soluble  in  liquid  ammonia.  The  preparations  were  heated 
in  vacuo  to  80°  and  then  dissolved  in  dilute  hydrochloric 
acid  preparatory  to  analysis. 

Analytical  results : 

I.  One-fourth  of  0.7520  g  of  substance  gave  0.2728  g 
CdS04  and  another  fourth  gave  0.0337  g  N. 

II.  One-half  of  0.1365  g  gave  0.1004  g  CdS04.  The  other 
half  gave  0.0124  g  N. 

III.  One-half  of  0.1232  g  of  substance  gave  0.0113  g  N 
and  the  other  half  gave  0,4910  g  Cd  by  electrolysis. 

IV.  One-half  of  0.3536  g.  gave  0.2549  g  CdS04.  The  other 
half  gave  0.0323  g  N. 


Calculated  for 

Cd(NH2)2 

Found 

I 

II 

III 

IV 

Cd 

N 

77.8 
19.4 

78.2 
18.0 

79-3 
18.2 

79-7 
18.3 

77-7 
18.2 

It,  therefore,  appears  that  cadmium  amide  is  formed 
by  the  action  of  potassium  amide  on  a  solution  of  a  salt  of 
cadmium  in  accordance  with  reactions  represented  by  the 
equations : 

Cd(CN)4K2  -h  2KNH2  ='  Cd(NH2)2  +  4KCN 
Cd(SCN)2  +  2KNH2  =  Cd(NH2)2  +  2KSCN 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        545 

The  fact  that  nitrogen  in  the  above  samples  runs  distinctly 
low  while  cadmium  shows  a  tendency  to  run  high  suggests 
that  a  small  amount  of  cadmium  imide  or  cadmium  nitride 
may  have  been  present  in  each  specimen. 

When  the  dry  amide  of  cadmium  is  exposed  to  moist  air 
it  immediately  assumes  an  orange  color  which  gradually  fades 
to  the  snow  white  of  cadmium  hydroxide.  The  yellow  ap- 
pearance may  be  due  to  the  initial  formation  of  cadmium 
oxide  or  possibly  of  a  mixed  base  of  the  formula  HO — Cd — NH2. 
When  pieces  of  cadmium  amide  come  in  contact  with  water 
they  dance  about  on  the  surface  of  the  Uquid  much  as  sodium 
does  but  without  sufficient  rise  in  temperature  to  produce 
incandescence.  When  heated  suddenly  to  a  high  tempera- 
ture, one  sample  exploded,  coating  the  glass  in  the  heated 
region  with  a  mirror  of  metallic  cadmium. 

3.  Cadmium  Nitride,  CdzN^} — When  cadmium  amide 
is  heated  to  180°  in  a  vacuum  it  loses  ammonia  and  is  con- 
verted into  cadmium  nitride  as  shown  by  the  following  analyses : 

I.  One-half  of  0.3041  g  of  substance  gave  0.0118  g  N 
and  the  other  half  gave  0.2549  g  CdS04. 

II.  One-half  of  0.1064  g  o^  substance  gave  0.0910  g 
CdS04.     The  other  half  gave  0.00437  g  N. 


Calculated  for 
CdaNa 

Found 

I 

II 

Cd 

N 

92.3 

7-7 

90.4 

7.8 

92.2 
8.2 

Just  as  metaUic  hydroxides  may  lose  water  when  heated 
to  form  oxides,  so  cadmium  amide  undergoes  deammonation 
to  form  the  nitride  as  represented  by  the  equation : 

3Cd(NH2)2  =  CdsNa  -f  4NH3 


1  Frantz  Fischer  and  Fritz  Schroter  [Ber.  deutsch.  chem.  Ges.,  43,  1465 
(1910)]  have  prepared  a  black  explosive  substance,  the  qualitative  analysis  of 
which  led  them  to  believe  they  had  cadmium  nitride  in  their  hands. 


546  George  S.  Bohart 

Cadmium  nitride  is  a  black,  apparently  amorphous 
substance  which  instantly  assumes  an  orange  color  when  ex- 
posed to  moist  air.  The  yellow  color  later  gives  place  to 
white  due  to  the  formation  of  cadmium  hydroxide,  A  small 
sample  of  the  nitride  exploded  violently  when  it  came  in 
contact  with  water.  Small  fragments  of  the  glass  container 
picked  up  after  the  explosion  were  found  to  be  covered  on 
one  side  with  a  mirror  of  metallic  cadmium. 

IV.    Action  of  Potassium  Amide  on  Potassium  Cyano- 

nickelate 

Attempts  to  prepare  a  pure  ammono  derivative  of  nickel 
by  treating  ammonated  nickel  iodide  with  potassium  amide 
resulted  in  failure.  The  difficultly  soluble,  blue  crystals  of 
the  nickel  salt  were  changed  to  a  red,  granular  mass  but 
analyses  showed  the  product  to  be  a  mixture  of  two  or  more 
compounds  which  could  not  be  separated. 

A  search  for  a  nickel  compound  which  could  be  obtained 
in  the  anhydrous  condition  and  which  would  be  at  the  same 
time  more  soluble  in  liquid  ammonia  than  nickel  iodide,  led 
to  the  discovery  that  potassium  cyanonickelate  could  be 
employed.  In  order  to  obtain  potassium  cyanonickelate  free 
from  potassium  carbonate,  with  which  it  is  often  contaminated^ 
the  following  method  was  devised : 

I.  Preparation  of  Pure  Potassium  Cyanonickelate, 
Ni{CN)4K2. — Nickel  sulfate  is  treated  with  enough  potassium 
cyanide  to  form  the  double  cyanide.  The  mixture  of  the 
cyanide  and  potassium  sulfate  in  solution  is  then  evaporated 
to  dryness  and  the  residue  extracted  with  Hquid  ammonia 
in  a  vacuum  jacketed  beaker.  Potassium  sulfate  and  any 
potassium  carbonate  which  may  have  been  present  in  the 
potassium  cyanide  are  entirely  insoluble,  whereas  potassium 
cyanonickelate  dissolves  in  about  its  own  weight  of  the  solvent. 
After  filtering  with  the  aid  of  a  vacuum  jacketed  funnel  and 
evaporating  the  ammonia  from  a  Dewar  beaker  receiver,  the 
salt  is  obtained  pure  as  a  light  yellow,   crystalline  residue. 

The  following  described  compounds  have  been  obtained 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        547 

as  the  result  of  treating  potassium  cyanonickelate  in  solution 
in  liquid  ammonia  with  potassium  amide. 

2.  Compound  No.  i.  A  Complex  Product  of  the  Empirical 
Formula  NizN2HiK^{CN)^.8NHz  and  its  Deammonation  Pro- 
duct, Ni3N<iH2K4{CN)e. — ^When  the  ammono  base  potassium 
amide  is  added  to  a  large  excess  of  potassium  cyanonickelate, 
a  brownish  red  solution  results  which  after  standing  fifteen 
minutes  to  a  half  hour  yields  a  crop  of  rather  large,  brownish 
red,  prismatic  crystals  which  have  been  found  to  have  the 
composition  represented  by  the  empirical  formula  Ni3NioH26- 
K4(CN)6.  The  crystals  readily  lose  ammonia  and  crumble 
to  a  light  yellow  powder  having  the  composition  represented 
by  the  formula  Ni3N2H2K4(CN)6. 

In  order  to  determine  the  amount  of  ammonia  of  crys- 
tallization thus  liberated,  each  leg  of  the  reaction  tube  pre- 
viously described  is  placed  in  a  bath  of  Hquid  ammonia  and 
after  connecting  with  the  apparatus  shown  in  Fig.  4  and 
opening  the  stopcock,  the  leg  containing  the  washings  is 
sealed  off.  While  the  leg  containing  the  pure  compound  is 
still  immersed  in  the  ammonia  bath  the  stopcock  is  connected 
to  an  air  pump  and  ammonia  is  removed  until  the  liquid  phase 
has  disappeared.  At  the  temperature  of  an  open  bath  of 
liquid  ammonia  the  vapor  tension  of  the  compound 
Ni3NioH26K4(CN)6  is  almost  zero.  When  the  manometer 
shows  that  a  constant  low  pressure  has  been  reached  the  stop- 
cock is  closed  and  the  tube  is  removed  to  a  balance  and 
weighed.  It  is  then  connected  with  the  air  pump  and  evacu- 
ated at  70°.  The  loss  of  weight  represents  the  amount  of 
ammonia  of  crystallization. 

The  analysis  of  the  deammonated  residue  offered  some 
difficulties  at  first  but  these  were  finally  overcome  by  the 
following  procedure:  A  silver  nitrate  solution  acidified  with 
nitric  acid  was  introduced  into  the  tube  containing  the  sample, 
whereby  the  latter  was  decomposed  according  to  the  equation : 

Ni3N2H2K4(CN)6  +  6HNO3  -I-  6AgN03  =  3Ni(N03)2  +  2NH4NO3  -|- 
4KNO3  +  6AgCN 


54^  George  S.  Bohart 

With  the  aid  of  the  apparatus  described  in  Fig.  5  the  solution 
containing  the  silver  cyanide  in  suspension  was  drawn  into 
a  small  flask.  The  silver  cyanide  was  filtered  off,  dried  and 
weighed.  The  excess  of  silver  was  precipitated  from  the  fil- 
trate as  the  chloride  and  removed  by  filtration.  In  order  to 
eliminate  nitric  acid  this  filtrate  was  treated  with  an  excess 
of  sulfuric  acid  and  evaporated  until  sulfuric  acid  fumes  be- 
gan to  appear.  The  solution  was  then  diluted  and  divided 
into  two  equal  portions.  In  one  half  nitrogen  was  determined; 
from  the  other  half  nickel  was  precipitated  electrol3rtically 
and  potassium  determined  from  the  residual  solution  as 
potassium  sulfate.  The  same  method  was  successfully  ap- 
plied in  the  analysis  of  the  two  nickel  compounds,  the  de- 
scription of  which  is  given  below. 

In  the  following  analytical  data,  Nos.  Ill  and  IV  were 
obtained  from  the  analysis  of  the  compound  containing  am- 
monia of  crystallization,  while  I,  II,  V  and  VI  represent 
analyses  of  the  deammonated  salt.  The  deammonated  prod- 
uct was  heated  to  about  70°  in  vacuo  preparatory  to  anal- 
ysis. 

Analytical  results : 

I.  The  specimen  which  weighed  0.5930  g  gave  0.0319  g 
N  and  0.2017  g  Ni. 

II.  The  specimen  weighed  0.3906  g  and  gave  0.4880  g 
Ag  from  the  decomposition  of  AgCN.  One-half  of  0.3906  g 
gave  0.0664  g  Ni. 

III.  Dried  in  vacuo  at  — 40°  the  specimen  weighed  1.0758 
g.  After  heating  to  70°  the  residue  weighed  0.8522  g  and 
gave  1.3280  g  AgCN. 

IV.  Dried  at  — 40°,  the  specimen  weighed  0.6417  g.  The 
deammonated  residue  weighed  0.51 15  g  and  gave  0.0274  S  N 
and  0.1743  g  Ni. 

V.  The  deammonated  specimen  weighed  0.5528  g  and 
gave  0.8560  g  AgCN.  One-half  of  0.5528  g  gave  0.0938  g 
Ni  and  0.1871  g  K2SO4.     The  other  half  gave  0.0147  S  N. 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        549 


NHo 


Calculated  for 

Ni8N2H2K4(CN)« 

Found 

I 

II 

III 

IV 

V 

Ni 
N 
K 
CN 

33-9 

5-4 

30.1 

30.1 

340 
5-4 

340 
30.1 

30.2 

34- 1 
5-4 

33-9 

5-3 

30.4 

30.0 

Calculated  for 
8NH3 

20.8 


20.8 


20.3 


The  analyzed  preparations  of  this  nickel  compound 
were  made  up  of  rather  large,  brownish  red,  prismatic  crystals 
of  very  uniform  size  and  shape.  The  analytical  results 
clearly  indicate  their  purity.  The  crystalline  substance  of 
the  formula  Ni3N2H2K4(CN)6.8NH3  shows  a  very  slight 
vapor  tension  at  — 40°  but  at  ordinary  temperature  all  of  the 
ammonia  of  crystallization  escapes  leaving  a  straw  yellow 
powder  of  the  composition  represented  by  the  formula 
Ni3N2H2K4(CN)6.  When  the  yellow  product  is  brought  into 
contact  with  water  it  dissolves  with  surprising  rapidity  but 
without  the  evolution  of  a  noticeable  quantity  of  heat.  When 
subjected  to  a  temperature  of  100°  it  begins  to  blacken  and 
decompose.  The  crystalHne  compound  is  sufficiently  soluble 
in  liquid  ammonia  to  give  the  solution  a  distinct  yellow  color. 

While  there  can  be  no  doubt  of  the  existence  of  definite 
compounds  of  the  empirical  formulas,  Ni3N2H2K4(CN)6.8NHa 
and  Ni3N2H2K4(CN)6,  the  question  of  their  constitution  is 
a  matter  which  has  not  been  satisfactorily  solved.  Following 
are  possible  formulas: 

K4Ni(CN)6.6NH3.2Ni(NH2)2  and  K4Ni(CN)6.2NiNH  or 
K2(CN)3Ni— NH— Ni— NH— Ni(CN)3K2.8NH3and 
K2(CN)3Ni— NH— Ni— NH— Ni(CN)3K2 

3.  Compound  No.  2.  A  Mixed  Cyanonickelate-Ammono- 
nickelate  of  Potassium,  K{CN)2NiNHK. — When  potassium 
amide  and  potassium  cyanonickelate  in  Uquid  ammonia  solu- 
tion   are   brought   together   in   approximately   equimolecular 


550 


George  S.  Bohart 


quantities  a  bright  yellow,  curdy  precipitate  instantly  ap- 
pears. It  is  necessary  to  wash  this  substance  very  rapidly, 
because  if  the  amount  of  the  nickel  salt  is  too  great  the  de- 
sired compound  becomes  contaminated  with  the  compound 
described  above,  whereas  if  an  excess  of  potassium  amide  is 
used  the  compound  No.  3,  described  below,  comes  down  with 
the  product  to  be  isolated.  In  spite  of  the  greatest  care, 
small  amoimts  of  these  compounds  did  contaminate  samples 
which  were  analyzed  and  the  results  are  somewhat  variable 
on  that  account.  The  substance  was  prepared  for  analysis 
by  heating  in  vacuo  to  80°  and  then  treating  in  a  manner 
described  for  the  analysis  of  the  above  compound.  No.  i. 
Analytical  results : 

I.  The  specimen  which  weighed  0.3385  g  gave  0.3468  g 
Ag  from  the  decomposition  of  AgCN.  One-half  of  the  speci- 
men gave  0.0107  g  N  and  the  other  half  gave  0.0472  g  Ni. 

II.  The  specimen  weighed  0.1980  g  and  gave  0.2020  g 
Ag  from  AgCN.  One-half  gave  0.0268  g  Ni  and  0.0837  S 
K2SO4.     The  other  half  gave  0.00608  g  N. 

III.  The  specimen  weighed  0.3130  g  and  gave  0.4135  g 
AgCN.  One-half  gave  0.0427  g  Ni.  One-fourth  gave  0.0672 
g  K2SO4  and  another  fourth  gave  0.00533  g  N. 


Calculated  for 

NiNHK2(CN)2 

Found 

I 

II 

III 

Ni 

N 

K 

CN 

28.8 

6.8 

38.4 

25-5 

27.9 
6.3 

24.7 

27.1 

6.1 

38.0 

24.6 

27-3 

6.8 

38.6 

25.6 

While  the  analytical  data  are  not  as  concordant  as  might 
be^desired  there  can  be  scarcely  any  doubt  that  the  products 
analyzed  were  specimens  of  a  compound  having  the  empirical 
formula  indicated.  The  constitution  of  the  conpound  seems 
fairly  clear.     It  is  potassium  cyanonickelate  which  has,   so 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        55 1 

to  speak,  been  half  converted  into  potassium  ammononickelate 
as  represented  by  the  equation : 

K(CN)2Ni(CN)2K  +  2KNH2  =  K(CN)2NiNHK  +  NH3  +  2KCN 

When  first  precipitated  this  compound  has  a  bright, 
lemon-yellow  color  and  presents  a  curdy  appearance.  It 
settles  rather  rapidly  and  after  one  or  two  washing  crumbles 
to  a  finely  divided  granular  material.  When  brought  into 
contact  with  water  it  dissolves  with  mild  sputtering  and  the 
evolution  of  a  slight  amount  of  heat. 

4.  Compound  No.  3.  A  Complex  Compound  of  the  Em- 
pirical Formula  NisNiiH^iK-jiCN)^. — When  potassium  cyano- 
nickelate  is  treated  with  a  large  excess  of  potassium  amide 
an  emerald-green  solution  results  which  after  a  few  minutes 
changes  to  a  deep  red  color.  At  the  end  of  an  hour  or  so 
crystals  begin  to  appear  on  the  walls  of  the  tube  in  which  the 
reaction  has  taken  place  and  after  the  lapse  of  about  twelve 
hours  the  solution  becomes  almost  colorless  while  a  crop  of 
red  crystals  adhere  to  the  glass.  After  washing  the  crystals 
were  treated  for  analysis  in  a  manner  described  under  Com- 
pound No.  I. 

Since  the  analysis  of  this  compound  led  to  such  an  ex- 
traordinary formula  it  was  considered  advisable  to  determine 
carbon  and  hydrogen  in  two  samples  by  combustion.  The 
analyses  given  in  III  and  IV  were  made  by  Mr.  L.  D.  KUiott 
of  this  laboratory  to  whom  the  writer  expresses  his  obligations. 
Previous  to  analysis  the  specimens  of  this  compound  were 
heated  to  70°  in  vacuo. 

Analytical  results : 

I.  A  specimen  weighing  0.3750  g  gave  0.1565  g  AgCN. 
One-half  of  the  specimen  gave  0.0426  g  N  and  the  other  half 
gave  0.0476  g  Ni  and  0.1684  §  K2SO4. 

II.  A  specimen  weighing  0.4033  g  gave  0.1281  g  Ag  from 
the  decomposition  of  AgCN.  One-half  gave  0.0526  g  Ni  and 
0.1803  g  K2SO4.     The  other  half  gave  0.0468  g  N. 

III.  A  specimen  weighing  0.0781  g  gave  0.0107  Z  CO2 
and  0.0227  g  H2O  by  combustion. 


552 


George  S.  Bohart 


IV.  The  specimen  weighing  0.1605  g  gave  0.0208  g  CO2 
and  0.0454  S  H2O  by  combustion. 


Found 

Calculated  for 

Ni3NiiH22K7(CN)2 

I 

II 

Ill 

IV 

Ni 

259 

25-4 

26. 1 

— 

— 

N 

22 

7 

22.8 

23.1 

— 

— 

K 

40 

4 

40.3 

40.2 

— 

— 

CN 

7 

7 

8.1 

7-7 

— 

— 

H 

3 

3 

— 

— 

3-2 

31 

C 

3 

5 

— 

— 

3-7 

3-6 

The  above  concordant  analytical  results  together  with 
the  fact  that  the  product  was  obtained  in  the  form  of  beautiful 
crystals  must  be  taken  as  conclusive  ^  proof  that  a  definite 
compound  of  the  empirical  formula  indicated  has  been  ob- 
tained. The  reaction  involved  in  its  formation  is  represented 
by  the  equation: 

3Ni(CN)4K2  +  11KNH2  =  Ni3NuH22K7(CN)2  +  loKCN 

Not  much  can  be  done  in  the  way  of  representing  the  con- 
stitution of  the  compound.  Of  a  considerable  number  of 
more  or  less  questionable  formulas  that  may  be  written  the 
formula  K(CN)2NiNHK.NH3.K2NNiNKNiNK2.6NH3,  is  per- 
haps the  most  satisfactory  in  that  it  represents  the  substance 
as  a  mixed  cyanonickelate-ammononickelate,  an  equimolecular 
combination  of  compound  No.  2  above ^  and  potassium  am- 
mononickelate  described  below.  It  may  also  be  represented 
by  the  formula  Ni(CN)2.2Ni(NH2)2.7KNH2. 

It  was  found  impossible  to  determine  ammonia  of  crys- 
tallization in  this  compound  by  the  usual  method  of  heating 
and  evacuating,  on  account  of  the  fact  that  no  sharp  line  of 

1  In  view  of  the  fact  that  all  the  compounds  belonging  to  the  group  of 
which  potassium  ammonozincate  is  a  typical  representative,  contain  sufficient 
ammonia  to  permit  their  formulation  either  as  salts  with  ammonia  of  crystalliza- 
tion or  as  molecular  compounds  of  the  amides  of  the  two  metals,  it  seems  probable 
that  a  compound  of  the  formula  K(CN)2.NiNHK.NH3  would  have  been  obtained 
had  the  preparation  No.  2  been  dried  at  low  temperature. 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        553 

division  exists  between  the  temperature  at  which  pure  am- 
monia comes  off  and  a  sHghtly  higher  temperature  at  which 
a  mixture  of  ammonia  and  another  undetermined  gas  escapes. 

This  compound  appears  as  bright,  red,  skeleton  crystals. 
Through  a  low  power  microscope  they  show  evidence  of 
homogeneity.  When  exposed  to  moist  air  they  soon  become 
coated  with  a  green  film  which  is  probably  nickel  hydroxide. 
In  contact  with  water  the  substance  sputters  vigorously  evolv- 
ing considerable  heat. 

In  connection  with  the  three  nickel  compounds  just  de- 
scribed, it  is  interesting  to  note  the  steady  decrease  in  the 
amount  of  the  cyanide  radical  as  the  content  of  potassium 
amide  increases. 

Compound  No.      I.     2KCN.2Ni(CN)2.Ni(NHK)2. 
Compound  No.    II.     2KCN.Ni(CN)2.Ni(NHK)2. 
Compound  No.  III.     Ni(CN)2.2Ni(NHK)2.3KHN2.4NH3. 

V.    Action  of  Potassium  Amide  on  Nickel  Sulfocyanate 

The  remarkable  results  obtained  by  the  action  of  potas- 
sium amide  on  potassium  cyanonickelate  led  to  a  search  for 
a  soluble  nickel  salt  free  from  cyanogen  in  order  to  avoid  the 
complications  encountered  in  the  work  above.  Finding  in 
ammonated  nickel  sulfocyanate  Ni(SCN)2.4NH3,  a  readily 
soluble  salt  and  one  which  may  be  easily  prepared  free  from 
water,  it  was  used  in  the  experiments  herewith  described. 

1.  Ammonated  Nickel  Sulfocyanate. — -A  specimen  of  a 
compound  which  was  thought  to  be  tetra- ammonated  nickel 
sulfocyanate,  Ni(SCN)2.4NH3,^  was  observed  to  be  different 
from  that  described  by  Meizendorff.  Upon  investigation 
it  was  found  to  have  the  composition  represented  by  the 
formula  Ni(SCN)2.3NH3.  A  further  search  led  to  the  dis- 
covery of  three  additional  ammonates  of  nickel  thiocyanate; 
one  having  two,  another  five  and  a  half,  and  a  third,  eight 
and  a  half  molecules  of  ammonia. 

2.  Nickel  Sulfocyanate  with  Four  Molecules  of  Ammonia, 
Ni{SCN)2-4NHz. — Preparation:     If  a  hot  saturated  solution 


Meizendorff:  Pogg.  Ann.,  56,  63  (1842). 


554 


George  S.  Bohart 


of  nickel  sulfate  is  treated  with  an  equivalent  amount  of 
ammonium  sulfocyanate  and  enough  ammonium  hydroxide 
solution  to  produce  a  strong  odor  of  ammonia,  the  color  of 
the  solution  changes  from  green  to  blue,  and  upon  cooUng  a 
crop  of  crystals  of  the  compound  Ni(SCN)2.4NH3  is  deposited. 

Nearly  all  of  the  nickel  sulfocyanate  from  the  mother 
liquor  may  be  recovered  by  evaporating  to  dryness  and  ex- 
tracting with  a  small  amount  of  concentrated  ammonium 
hydroxide  solution.  The  success  of  this  separation  depends 
upon  the  fact  that  nickel  sulfocyanate  is  much  more  soluble 
in  concentrated  ammonium  hydroxide  solution  than  is  am- 
monium sulfate. 

If  a  strong  ammonium  hydroxide  solution  of  nickel  sulfo- 
cyanate is  exposed  to  the  air  until  the  excess  of  ammonia  has 
escaped,  most  of  the  solute  is  deposited.  This  is  to  be  ex- 
pected since  nickel  sulfocyanate  is  much  more  soluble  in 
liquid  ammonia  than  in  water. 


Axial  ratio :  a  :  b  : 

c  =  1.398  :  ] 

:  0.687.     |9  = 

75°  41' 

Angle 

No.  measured 

Measured 

Calculated! 

mm 

(no  :  ilo) 

19 

107°  7' 

107°  7' 

mm 

(no  :  iio) 

20 

72°  53' 

PP 

(hi  :  in) 

14 

57°  30' 

PP 

(in  :  in) 

9 

122°  39' 

122"  40' 

mp 

(no  :  in) 

7 

45°  28' 

45  °  20' 

my 

(no  :  201) 

4 

68°  41' 

69°  7' 

my 

(no  :  201) 

4 

ni°3' 

110°  53' 

ma 

(no  :  100) 

15 

53°  32' 

52,°  33' 

cp 

(001  :  in) 

7 

35°  39' 

36°  12' 

mc 

(iio  :  001) 

7 

98°  36' 

98°  28' 

bp 

(010  :  in) 

2 

62°  25' 

62°  20'^ 

ay 

(100  :  201) 

7 

52°  47' 

53°  7' 

cy 

(001  :  201) 

10 

5i°32' 

51°  12' 

ap 

(100  :  in) 

7 

57°  42' 

57°  46' 

ac 

(100  :  001) 

6 

75°  40' 

75°  41' 

ac           (loo  :  ooij 

7 

104°  19' 

1  Dull  faces  resulting  from  the  instability  of  ammoniated  nickel  sulfocy- 
anate in  moist  air  was  responsible  for  the  lack  of  closer  agreement  between  the 
measiu'ed  and  calculated  values  for  the  angles. 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        555 


Crystals  suitable  for  measurement  on  the  reflection  gon- 
iometer were  obtained  by  making  a  saturated  solution  in  a 
liquid  made  up  of  one  part  of  concentrated  ammonium  hy- 
droxide solution  to  four  parts  of  water  and  exposing  to  the  air 
for  twelve  hours. 

Crystallography:^  Crystals  of  this  compound  belong  to 
the  monoclinic  system.     Prismatic  class.     A2.P.(C). 

Listof  forms:w(iio),;^(iii),:v(2oi),a(ioo),c(ooi),  6(010). 
The  faces  shown  in  Fig.  6  are  those  which  are  found  on  the 
typical  crystal.  Faces  a (100)  and  6(010)  are  usually  either 
very  narrow  or  missing.  Physical  properties:  Color,  sap- 
phire-blue. Luster,  vitreous.  Cleavage,  perfect  parallel 
to  w(iio)  and  ^'(201).  Solubility,  slightly  soluble  in  an  aque- 
ous solution  of  ammonium  sulfocyanate  but  decomposed  by 
pure  water.  This  behavior  may  be  explained  by  the  equation : 
Ni(SCN)2  +  2NH4OH  ^=i  Ni(0H)2  +  2NH4SCN 

The   solubility   in   liquid   ammonia   is   very   great.     In   con- 
centrated ammonium  hydroxide  solution  about  60  g  dissolve 


m 


m  \ 


,<C^ 


\Tn 


FIG.  6 
NifSCN)^'4NH^ 


riG.J 
NifSCNL'dNH^ 


in  100  cc  at  18°.     StabiHty :   The  crystals  are  unaltered  by  dry 
air  but  rapidly  lose  their  luster  and  turn  green  in  moist  air. 

3.  Nickel  Sulfocyanate  with  Three  Molecules  of  Ammonia, 


1  The  crystallography  given  in  this  paper  was  done  at  the  suggestion  and 
tinder  the  direction  of  Professor  A.  F.  Rogers  of  the  Leland  Stanford  Junior 
University. 


556 


George  S.  Bohart 


Ni{SCN)2.3NH3. — Preparation:  If  a  saturated  solution  of 
the  above  described  compound,  Ni(SCN)2.4NH3,  containing 
a  small  amount  of  ammonium  sulfocyanate  is  exposed  to  the 
air  for  a  few  hours,  crystals  having  a  deeper  blue  color  begin 
to  appear  and  grow  at  the  expense  of  the  lighter  blue  com- 
pound if  the  latter  is  present.  Analysis  showed  the  deeper 
blue  compound  to  be  a  substance  represented  by  the  formula 
Ni(SCN)2.3NH3.^ 

In  the  absence  of  ammonium  sulfocyanate,  nickel  sulfo- 
cyanate with  three  molecules  of  ammonia  does  not  form. 
This  behavior  results  from  a  reaction  expressed  by  the  equation : 

Ni(SCN)2  +  2NH4OH  ^^^  Ni(0H)2  -f  2NH4SCN 
Crystallography:     Crystals  of  this  compound  belong  to  the 
orthorhombic  system.     Bipyramidal  class.     3A2.3P.(C) 

Axial  ratio:  a  :  b  :  c  =  0.948  :  i  :  0.702 


Angle 

No.  measured 

Measured 

Calculated 

bm 

(010  :  no) 

37 

46°  31' 

be 

(010  :  on) 

14 

54°  55' 

55!"; 

mm 

(no  :  no) 

23 

86°  57' 

86°  58' 

ce 

(ooi  :  on) 

20 

34°  49' 

34°  46' 

ma 

(no  :  100) 

2 

43°  22' 

43°  29' 

cp 

(001  :  in) 

5 

45°  16' 

45°  14' 

mp 

(no  :  in) 

5 

44°  46' 

mz 

(no  :  114) 

I 

75°  10' 

75°  49' 

List  of  forms:  a(ioo),  fc(oio),  c(ooi),  ^(01 1),  w(iio),  ^(iii)^ 
2(114).  The  faces  shown  in  Fig.  7  are  those  which  are  found 
on  the  typical  crystal.  Forms  p{iii)  and  a(ioo)  are  of  com- 
paratively rare  occurrence  and  2(114)  was  found  on  one  crystal 
only. 

Physical  properties:  Color,  deep  blue.  Luster,  vitreous. 
Cleavage,  absent.  Solubihty  and  stability,  similar  to  nickel 
sulfocyanate  with  four  molecules  of  ammonia. 

Analytical  results : 

I.  A  specimen  weighing  0.2329  g  gave  0.4824  g  BaSO* 
and  0.0526  g  NH3. 

^  Ber.  deutsch.  chem.  Ges.,  41,  3178  (1908). 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        557 

II.  A  specimen  weighing  0.1892  g  gave  0.3915  g  BaS04 
and  0.0424  g  NH3. 


Calculated  for 
Ni(SCN)2.3NH3 

Found 

I 

II 

SCN 
NH3 

514 
22.6 

515 
22.6 

515 
22.5 

4.  Nickel  Sulfocyanate  with  Two  Molecules  of  Ammonia, 
Ni{SCN)2.2NH3. — Preparation:  When  an  aqueous  solution 
of  nickel  sulfocyanate  in  which  a  considerable  amount  of 
ammonium  sulfocyanate  has  been  dissolved  is  left  exposed 
to  the  air  for  a  few  weeks,  a  compound  having  the  composi- 
tion represented  by  the  formula  Ni(SCN)2.2NH3  is  formed. 
The  crystals  obtained  were  not  suitable  for  measurement  on 
the  reflection  goniometer. 

Physical  properties:  Color,  greenish  blue.  Luster,  vit- 
reous. SolubiHty  and  stabiUty,  similar  to  tetra-ammoniated 
nickel  sulfocyanate. 

Analytical  results : 

I.  A  specimen  weighing  0.2246  g  gave  0.5003  g  BaS04 
and  0.0364  g  NH3. 

II.  The  specimen  weighed  0.2214  g  and  gave  0.4949  g 
BaS04  and  0.0358  g  NH3. 


Calculated  for 

Ni(SCN)2.2NH, 

Found 

I 

II 

SCN 
NH3 

55-5 
16.3 

55-5 
16.2 

55-6 
16.2 

5.  Nickel  Sulfocyanate  with  Five  and  a  Half  Molecules  of 
Ammonia,  Ni{SCN)2.5^/2NHz. — Preparation:  If  a  concen- 
trated ammonium  hydroxide  solution  is  sattuated  with  nickel 
sulfocyanate  at  about  20°  after  which  the  temperature  is 
lowered  a  few  degrees,   a  crop  of  large,  beautiful,  tabular 


558 


George  S.  Bohart 


crystals  appear.  On  account  of  their  efflorescent  nature  these 
crystals  were  not  measured  on  the  reflection  goniometer. 

Physical  properties:  Color,  blue  with  a  violet  tone. 
Luster,  vitreous.  SolubiUty,  similar  to  tetra-ammoniated 
nickel  sulfocyanate.  Stability,  when  removed  from  the 
mother  liquor  and  exposed  to  moist  air,  crystals  of  this  com- 
pound instantly  lose  their  luster  and  begin  to  lose  ammonia. 

Analytical  results:^ 

I.  A  specimen  weighing  0.2064  §  gave  0.0174  g  NH3 
and  0.3580  g  BaS04. 

II.  A  specimen  weighing  0.2715  g  gave  0.0940  g  NH3 
and  0.4715  g  BaS04. 

III.  A  specimen  weighing  0.1586  g  gave  0.0551  g  NH3 
and  0.2751  g  BaS04. 

IV.  A  specimen  weighing  0.1946  g  gave  0.0679  S  NH3. 


Calculated  for 

Ni(SCN)2.5V2NH8 

Found 

I 

II 

III 

IV 

SCN 
NH3 

43-3 
34-9 

43-2 
34-6 

43   I 
34-6 

•       43-2 
34-8 

34-9 

6.  Nickel  Sulfocyanate  with  Eight  and  a  Half  Molecules 
of  Ammonia,  Ni{SCN)2.8^/2NH3. — Preparation:  When  a  tube 
containing  a  liquid  ammonia  solution  of  nickel  sulfocyanate 
is  immersed  in  an  open  bath  of  liquid  ammonia,  and  ammonia 


1  Working  at  o°  with  a  specimen  of  nickel  sulfocyanate  weighing  in  the 
neighborhood  of  0.037  S>  Walter  Peters  [Ber.  deutsch.  chem.  Ges.,  41,  3178 
(1908)]  obtained  results  which  led  him  to  believe  that  he  had  a  compound  with 
the  composition  represented  by  the  formula  Ni(SCN)2.6NH3. 

With  the  hope  of  obtaining  the  same  compound,  a  sample  of  nickel  sul- 
focyanate weighing  o.  1 640  g  was  dissolved  in  liquid  ammonia  and  the  tube  con- 
taining the  solution  was  connected  to  a  suction  pump  where  it  was  evacuated 
at  0°.  After  the  pressure  had  steadily  fallen  from  21  cm  (the  vapor  tension  of 
the  compound  Ni(SCN)2.8V2NH3  at  0°)  to  nearly  zero,  the  specimen  was  found 
to  weigh  0.2539  g.  The  formula  of  the  compound  calculated  from  these  re- 
sults would  be  Ni(SCN)2.5.6NH3,  which  agrees  closely  with  the  formula  of  the 
compound  having  five  and  a  half  molecules  of  ammonia.  In  spite  of  careful 
observation  the  pressure  in  the  manometer  gave  no  indication  of  the  existence 
of  an  ammoniated  nickel  sulfocyanate  having  six  molecules  of  ammonia. 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        559 


is  removed  from  the  solution  until  the  Hquid  phase  has  dis- 
appeared, a  crystalline  residue  is  obtained. 

Physical  properties:  Color,  similar  to  the  compound 
having  five  and  a  half  molecules  of  ammonia.  Stability, 
at  — 40°  the  vapor  tension  is  about  7.5  cm.  At  laboratory 
temperatiu-e  the  compound  rapidly  loses  ammonia  and  goes 
over  to  the  modification  having  five  and  a  half  molecules  of 
ammonia. 

Analytical  results : 

A  specimen  of  Ni(SCN)2.5V2NH3  weighing  0.2520  g 
was  dissolved  in  liquid  ammonia  and  the  tube  containing  the 
solution  was  placed  in  an  open  ammonia  bath  and  connected 
to  a  suction  pump.  Ammonia  was  removed  until  the  pressure 
became  constant  at  about  7.5  cm,  after  which  the  tube  with 
its  contents  were  weighed.  This  entire  procedure  was  re- 
peated three  times. 


Calculated  wt.  for 

Ni(SCN)2.8V2NH3 


Found 


II 


III 


0.2999  g  0.2991  g  0.2990  g  0.2986  g 

7.  Potassium  Ammonickelate,  NiJSIzK^.dNHz. — ^When  the 
ammonia-soluble  nickel  sulfocyanate  is  treated  with  a  large 
excess  of  potassium  amide  a  deep  red  solution  is  formed  from 
which  a  red,  crystalline  product  is  slowly  deposited.  After  a 
few  hours  the  liquid  becomes  nearly  colorless.  The  crop 
of  crystals  may  be  readily  freed  from  soluble  impurities  by 
four  or  five  washings  with  pure  liquid  ammonia.  For  analysis 
the  crystals  were  heated  in  vacuo  to  50°  and  dissolved  in  sul- 
furic acid. 

Analytical  results : 

I.  One-half  of  0.4967  g  of  the  compound  gave  0.0633 
g  Ni  and  the  other  half  gave  0.0673  g  N. 

II.  One-half  of  0.5684  g  of  substance  gave  0.0724  g  Ni 
and  0.2730  g  K2SO4.     The  other  half  gave  0.0808  g  N. 

III.  One-half  of  0.3253  g  sample  gave  0.0425  g  Ni  and 
0.1558  g  K2SO4.     The  other  half  gave  0.0449  Z  N. 


56o 


George  S.  Bohart 


Calculated  for 
NizNgHisKs 

Found 

I 

II 

III 

Ni 

N 

K 

25-7 
27.6 
42.8 

25-5 
27.0 

25-5 
28.4 

43-1 

26. 1 
27.7 
42.9 

The  compound,  to  which  either  of  the  formulas 
K2N— Ni— NK— Ni— NK2.6NH3  or  2Ni(NH2)2.5KNH2  may 
be  given,  is  obviously  a  member  of  the  same  group  of  compounds 
to  which  potassium  ammonocadmiate,  described  above,  be- 
longs. The  reaction  whereby  potassium  ammononickelate 
is  formed  may  be  represented  by  the  equation : 

2Ni(SCN)2  +  9KNH2  =  NigNgHisKs  +  4KSCN 

This  compound  is  obtained  in  the  form  of  rather  small, 
red  crystals  resembhng  those  of  Ni3NiiH22K7(CN)2  in  general 
appearance.  It  is  sufficiently  soluble  in  liquid  ammonia  to 
give  the  solution  a  pale  red  color.  When  brought  into  con- 
tact with  water  it  reacts  vigorously  with  the  evolution  of  con- 
siderable heat. 

8.  Nickel  Amide,  Ni{NHz)2. — With  a  solution  of  potas- 
sium amide  nickel  sulfocyanate  in  excess  yields  a  red,  floccu- 
lent  precipitate.  In  order  to  ensure  the  purity  of  this  sub- 
stance it  must  be  thoroughly  washed.  The  analyses  of  the 
two  following  samples  were  made  after  heating  in  vacuo  to 
40°  and  dissolving  in  dilute  sulfuric  acid: 

I.  One-half  of  0.2242  g  of  substance  gave  0,0730  g  Ni 
and  the  other  half  gave  0.0335  S  N. 

II.  One-half  of  o.  16 13  g  gave  0.0522  g  Ni  and  the  other  half 
gave  0.0250  g  N. 


Calculated  for 

Ni(NH2)2 

Found 

I 

II 

Ni 
N 

64.7 
30.9 

65.1 
29.9 

64.7 
310 

Potassium  Amide  and  Salts  of  Cadmium,  Etc.        561 

The  formation  of  nickel  amide  is  expressed  by  the  equation : 

Ni(SCN)2  +  2KNH2  =  Ni(NH2)2  +  2KSCN 

It  is  obtained  as  an  insoluble,  flocculent,  terra-cotta  red 
substance  which  settles  rather  rapidly  in  liquid  ammonia. 
After  long  continued  washing  it  shows  a  tendency  to  go  over 
into  the  colloidal  condition.  It  reacts  rather  mildly  with 
water,  forming  nickel  hydroxide  and  free  ammonia. 

p.  Nickel  Nitride,  NisN^. — When  nickel  amide  is  heated 
to  about  120°  in  vacuo  a  slow  evolution  of  ammonia  occurs. 
Unfortunately,  however,  a  secondary  reaction  takes  place 
to  a  certain  extent  whereby  free  nitrogen  is  liberated.  In 
the  analysis  of  Samples  I  and  II  given  below  it  will  be  seen 
that  nickel  runs  high  while  nitrogen  runs  low.  The  nitrogen 
given  off  in  the  above-mentioned  secondary  reaction  was 
measured  in  Sample  III. 

I.  One-half  of  0.1572  g  of  substance  gave  0.0693  8  Ni. 
The  other  half  gave  0.00701  g  N. 

II.  One-half  of  0.1682  g  gave  0.1981  g  NiS04.  The  other 
half  gave  0.00837  g  N. 

III.  One-half  of  0.0864  §  gave  0.00646  g  N.  The  other 
half  gave  0.047  S  NiO.  The  nitrogen  gas  collected  in  an  eudi- 
ometer measured  3.75   cc  over  water  at  23°  and  760  mm. 


Calculated  for 

NisNi! 

Found 

I 

II 

III 

Ni 
N 

86.3 
13-7 

88.2 
8.9 

89.2 
lO.O 

85.5 

14.9 

The  reactions  whereby  nickel  nitride  is  formed  from  the 
amide  is  analogous  to  the  formation  of  nickel  oxide  from 
nickel  hydroxide  and  is  represented  by  the  equation : 

3Ni(NH2)2  =  Ni3N2  +  4NH3 

Nickel  nitride  is  a  black,  apparently  amorphous  substance 
which  reacts  with  water  very  slowly  if  at  all.     It  dissolves 


562  George  S.  Bohart 

slowly  in  dilute  acids  producing  ammonium  and  nickel  salts 
of  the  acid  used. 

NisNs  +  8HC1  =  3NiCl2  +  2NH4CI. 
At  about  120°  it  slowly  decomposes  into  its  constituent  ele- 
ments. 

VI.    Action  of  Potassium  Amide  on  Ammonium  Chromium 
Sulfoeyanate,  NH4Cr(SCN)4.2NH3 

Since  the  double  ammonium  chromium  sulfoeyanate  is 
very  soluble  in  liquid  ammonia  an  attempt  was  made  to  de- 
termine the  effect  of  potassium  amide  on  its  solution.  Small 
additions  of  the  ammono  base  cause  the  separation  of  a  dense, 
wine-red,  gelatinous  substance.  With  the  addition  of  further 
quantities  of  potassium  amide  the  deep  red  color  of  the  original 
solution  is  completely  discharged  and  a  beautiful  salmon 
pink,  flocculent  precipitate  appears.  If  now  a  shghtly  greater 
amount  of  potassium  amide  is  added,  the  flocculent  material 
takes  on  a  dull  purple  color.  With  a  large  excess  of  the  base 
the  flocculent  precipitate  dissolves,  forming  a  wine-red  solution 
which  later  yields  a  crop  of  small  crystals  of  the  same  color. 
A  microscopic  examination  of  these  crystals  indicate  the  pres- 
ence of  two  different  compounds.  Several  analyses  showed 
this  material  to  be  composed  of  ammono  chromites.  Not- 
withstanding numerous  attempts  it  has  also  been  found  im- 
possible to  prepare  either  of  the  flocculent  precipitates  men- 
tioned above  in  a  pure  condition. 

VII.    Summary 

When  treated  with  potassium  amide  in  liquid  ammonia 
solution,  cadmium  sulfoeyanate  and  potassium  cyanocadmiate 
yield  either  cadmium  amide,  Cd(NH2)2,  or  potassium  am- 
monocadmiate,  Cd(NHK)2.2NH3,  depending  upon  whether 
the  cadmium  salt  or  the  ammono  base  is  in  excess.  When 
cadmium  amide  is  heated  above  180°  it  is  converted  into  the 
nitride. 

Potassium  cyanonickelate  yields  three  distinct  compounds 
when  treated  with  potassium  amide.  With  the  salt  in  large 
excess,  a  brownish  red,  slightly  soluble,  crystalline  substance 
is  obtained  having  the  formula  Ni3N2H2K4(CN)6.8NH3.     At 


Potassium  Amide  and  Salts  of  Cadmium,  Etc.        563 

ordinary  temperature  and  pressure  the  eight  molecules  of 
ammonia  escape,  leaving  a  straw-yellow  powder,  of  the  compo- 
sition represented  by  the  formula  Ni3N2H2K4(CN)6. 

When  approximately  equivalent  amounts  of  potassium 
cyanonickelate  and  potassium  amide  are  brought  together, 
a  lemon-yellow,  curdy  precipitate  is  formed.  After  a  few 
washings  with  liquid  ammonia  this  substance  crumbles  to 
a  heavy  powder  having  the  composition  K(CN)2 — Ni — NHK. 

If  a  large  excess  of  potassium  amide  is  used  the  lemon- 
yellow  product  first  formed  dissolves,  forming  a  deep  red  solu- 
tion which  upon  standing  twelve  hours  or  so  yields  a  crop  of 
deep  red  crystals  having  the  composition  Ni3NuH22K7(CN)2. 

By  varying  the  concentration  of  ammonia  in  ammonium 
hydroxide  solutions  of  nickel  sulfocyanate,  the  following  crys- 
talUne  modifications  of  ammoniated  nickel  sulfocyanate  may 
be  prepared:  Ni(SCN)2.2NH3;  3NH3;  4NH3;  5V2NH3.  A 
fifth  modification  having  eight  and  a  half  molecules  of  ammonia 
Ni(SCN)2.8V2NH3  may  be  prepared  by  removing  the  liquid 
phase  from  a  liquid  ammonia  solution  of  nickel  sulfocyanate 
while  the  temperature  is  kept  at  about  — 40°. 

A  liquid  ammonia  solution  of  nickel  sulfocyanate  gives  a 
precipitate  of  nickel  amide  Ni(NH2)2  when  treated  with  an 
equivalent  amount  of  potassium  amide.  Nickel  amide  is 
soluble  in  an  excess  of  potassium  amide,  however,  producing 
a  deep  red  solution,  from  which  a  compound  having  the 
formula  Ni2N3K5.6NH3  crystallizes  out.  If  heated  above 
120°  nickel  amide  is  converted  to  the  nitride. 

When  ammonium  chromium  sulfocyanate,  NH4Cr(SCN)4.- 
2NH3  is  treated  with  varying  amounts  of  potassium  amide, 
several  different  products  appear.  On  account  of  the  difficulty 
of  getting  any  one  of  them  in  a  pure  condition  they  have  not 
been  isolated. 

This  work  was  done  in  the  chemical  laboratory  of  the 
Leland  Stanford  Junior  University  at  the  suggestion  and  under 
the  direction  of  Professor  E.  C.  Franklin. 

Stanford  University 

California 

April  I,  1Q14 


M>     »«1*** 


'^^t^'^m^i-^,k 


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